This invention concerns a polymeric adsorbent material comprising a post-crosslinked polymer as a substrate which has been surface-modified with at least one polymer and to a process for preparing such polymeric adsorbent materials. The polymeric adsorbents have controlled pore geometry and variable chemical functionality. The polymeric adsorbents may have an interpenetrating polymer network.
The rapid advances in bio-technology along with consumers' desire for tastier, healthier, and more esthetically pleasing food and beverage products have created urgent needs for highly selective, efficient, and cost-effective processes for separating various chemicals from complex mixtures. Environmental concerns for cleaner air, water and soil have further increased a demand for better and improved separation systems. Thus, the demand for better separation materials is rapidly moving beyond the realm of the conventional adsorbents and membranes.
Interpenetrating polymer networks (IPN) using polystyrene/polystyrene as models for ion-exchange resin matrices (IER-IPN) were first introduced in the sixties (see for example, J. R. Millar, Journal of Chemical Society, p. 1311 (1960); p. 1789 (1962); and p. 218 (1963)). More recently, IER-IPNs have been described in "Sulfonic Acid Resins With interpenetrating Polymer Networks", in D. Klempner and K. C. Frisch, Ed., Advances in Interpenetrating Polymer Networks, Volume II, Technomic Publishing Co., Inc., Lancaster, Basel, (1990), pp. 157-176.
One of the drawbacks in IPN technology has been the necessity of the first crosslinked polymer to adsorb, imbibe, or swell in the monomer or second polymer to create molecular interpenetration. Until now, molecular interpenetration was thought to occur only in the cases where two or more polymer phases within the IPN possessed similar solubility characteristics or solubility parameters. In the case of crosslinked polymer substrates, the substrate polymer is either insoluble or swells in the presence of a compatible monomer or polymer possessing similar solubility parameters. Depending on the free energy of mixing, the crosslinked polymer either phase separates or fails to imbibe the monomer or second polymer (see for example, C. H. Sperling, Interpenetrating Polymer Networks and Related Materials, Plenum Press, New York, (1981)).
Another drawback to conventional IPNs prepared from conventional highly crosslinked adsorbents is the loss in porosity as the pores of the first polymer are filled with the monomer or second polymer. The final pore distribution in these IPNs is determined by the amount of the second polymer and the mixing thermodynamics governed by the Flory Huggins theory.
Polymeric adsorbents and ion exchange resins of macronet type polymers (post-crosslinked) are described in U.S. Pat. Nos. 4,263,407 and 4,191,813. These patents teach that the macronet adsorbents obtained from macroreticular (macroporous) copolymers may be used as substrates for hybrid copolymers and ion exchange resins. In a method for preparing the hybrid copolymers and ion exchange resins, a liquid monomer mixture containing a crosslinking monomer is added to an aqueous suspension of the macronet adsorbent, which liquid mixture is imbibed into the pores of macronet adsorbent and is polymerized therein. The resulting hybrid product may then be converted into an ion exchange resin by appropriate functionalization in the conventional manner.
It is an object of this invention to provide surface-modified adsorbent materials which have useful surface area, desired porosity, surface functionality and physical properties for a variety of chromatographic separations.